Method of dyeing yarn with indigo



March 8, 1938. w. c. Foss METHOD 0F DYEING'YARN WITH INDIGO Filled Aug. 12, 1955 2 sheets-sheet 1 E LQ Inl/enfer.'

March 8, 1938. W. C. FOSS 2,110,595

METHOD oF DYEING YARN WITH INDlGo Filed Aug. 12; 195e 2 sheets-sheet 2 Patented Mar. 8, 1938 v METHOD OF DYEING -YARN' WITH INDIGO Wilfred C. Foss, Greenvllle,-N. H., asslgnor to Otis l Company, Ware, Mass., a corporation of Massaohusetts Application August 12, 1936, Serial No. 95,533

2 Claims.

vIn preparing cotton yarn for the manufacture of denim or other cloth, the yarn is dyed with indigo. In accordance with the dyeing practice prior to the present invention, the yarn was prepared for the dyeing operations by passing it through a vat containing hot dilute sodium hydroxide solution to remove oils and other undesirable materials, and then cooling it by spraying A each thread.

with cool water. The yarn, thus prepared, was coated with a reduced indigo solution and the coating oxidized. For this purpose, successive portions vof a given'length of yarn were passed through a reduced indigo liquor to coat the threads of the yarn, then through Isqueeze rolls to remove surplus liquor and then through an air space to oxidize the coating. The length of yarn was fed continuously at such rate that a given point on the yarn was immersed in the liquor about one-half minute and subsequently exposed to the air about one-half minute to oxidize the indigo coating. Each immersion of the yarn in the liquor has been known as a dip. It has been the bestpractice to subject the yarn to eight dips, each followed by oxidation of the indigo, Where'- by `eight coatings have been superimposed upo A common fault of indigo dyed goods of all descriptions has been the gradual formation of white spots in the cloth when the cloth is subjected to wear. The formation of these white spots has been caused by wearing through the indigo coatings on the threads, thus exposing the white threads. This can be demonstrated by rubbing local spots with sandpaper' whereupon white spots will appear. It has been obvious to those skilled in the art of indigo dyeing that this fault could be overcome by causing the indigo dye to penetrate the threads and coat the indi'- vidual strands or bres of which the threads are lcomposed or even penetrate such bres. No one, however'y has been 'able to suggestion a solution for this problem or a practical and commercially usable method for causing the indigo dye to penetrate the threads.

It is an object of lthe present invention to provide a commercially practical' method for dyeing yarn with indigo so that the dye will penetrate the threads of the yarn. 1 A

The invention will be more clearly understood from the following description vin conjunction with the accompanying drawings: in which,

Fig. l is a diagrammatic longitudinal eleva.-` tional view of a suitable apparatus for use in carrying'out certain of the steps of the method of the invention;

Fig. 2 is` a diagrammatic longitidinal elevational vie'w of another apparatus suitable for use in carrying out other steps of t e method of the invention; and

Flgs.3 to '7 inclusive'are diagrammatic longitus-shown in Fig. 1 illustrating steps in the practice of the invention.

In the practice of the invention the length of yarn, which for the purpose of illustration is assumed to be 1000 yards, is first wetted out by passing through a hot dilute sodium hydroxide solution in the usual manner. It is then passed through squeeze rolls and subjected to the action of a spray of cool water,v after4 which it is run through squeeze rolls to remove the surplus of water. This is a common procedure for the preliminary treatment of yarn prior to dyeing with indigo. The purpose of this treatment with the hydroxide of sodium is to remove oils and other undesirable materials in the yarn and the purpose of the treatment with the cool water is to cool the yarn so as to prevent it drying out. The present invention devlates from the usual practice at this point.

In accordance with the present invention a given length of previously wetted out yarn 9 is fed from a box it over a roll l l and thence down into a vat i2 containing reduced indigo solution, namely,` a liquor composed essentially of water, indigo and hydrosulfite of soda. The yarn 9 is guided through' the liquor in the vat l2 by rolls i3, it, i5, it and il and then is moved upwardly out of the vat i2 over a roll I8, and then over a roll i9 carried by a traverse mechanism T. The yarn moves downwardly from the roll i9 into a vat B asindicated by the arrow in Figs. l and 3. The traverse mechanism T moves longitudinally of the apparatus and traversely thereof so as to permit the yarn to be laid in the vat in strands extending back and forth longitudinally of the 'vat and in layers of strands extending across the vat so as to prevent entanglement of the strands.

As successive portions of the given length of yarn is fed into the vat B they are permitted tov remain in a slack condition in the reducedindigo liquor during the feeding into the vat of the remaining portions of the given length ofyarn.

As the rear end of the given length of yarn is about to pass into the reduced indigo solution in the vat B the direction of movement of the yarn is reversed so that the yarn is caused to move out of the vat B and over the roller I9 and thence over the roller 20 carried by the traverse mechanism T (Fig. 4) and is then permitted to drop the yarn u ntil after the iinal immersion.

into a reduced indigo liquor contained in the vat C and be laid therein in strands extending back and forth longitudinally in the vat and in layers of strands extending across the vat. As successive portions of the given length of yarn is fed into the vat C they are permitted to remain in a slack condition in the reduced indigo solution during the feeding into the vat yof the remaining' portions of the given length of yarn.

As the end of the given length of yarn is about to pass into the liquor in the vat C the move.- ment of the yarn is reversed and the given length of yarn is moved out of the liquor in the vat C and is caused to pass through squeeze rolls S for removing surplus liquor. From the squeeze rolls S the yarn is moved upwardly in open air and over a roll 2l carried by a traverse mecha-I nism T similar to the traverse mechanism T. The yarn passes downwardly from the roll 2i through the open air and into a box 22 where it is laid in strands extending back and forth longitudinally of the box and in layers of strands ex tending across the box. As the given length of yarn passes through the squeeze rolls S through the air and into the box 22, the reduced indigo, which has penetrated the yarn, is oxidized.

If desired, instead of withdrawing the length of yarn from the vat C and passing it through the squeeze rolls S as described, the yarn may be returned in the opposite direction over the rolls and i9 and downwardly into the vat B.

p As the end of the yarn is about to pass into the vat B it is withdrawn from the vat B and fed over the rolls I9 and 2D and thence downwardly into the reduced indigo liquor in the vat C. This optional procedure affords a longer time for the penetration of the indigo into the yarn. The yarn is then withdrawn from the vat C and passed through the squeeze rolls S and moved upwardly over the roll 2| and downwardly into the box 22. i In order to secure uniform dyeing and desire penetration of the dye in the threads of the yarn the time of immersion of all portions of the given length of yarn should be substantially equal and the yarn, preferably, should be as free from tension as possible. This is accomplished in the practice of the invention by feeding the given length of yarn at least twice into a dye vat so that it drops into the dye liquor by gravity and is withdrawn solely against the action of gravity and the surplus liquor is not removed from Inasmuch as successive portions of the yarn are permltted to remain in a slack condition in a given location in the dye liquor While the remaining portions are fed thereto, the time of immersion for all portions of the -given length of yarn is the same and is equal at least toy about one-half the time required for the entire immersion operation. Ifthe rate of movement of the yarn is the same as that used in dyeing practice prior to the invention, the time required for Athe entire treatment is about the same.. Nevertheless, by the practice of the invention each successive portion of the yarn is immersed in the dye liquor at least fifteen times as long asin the prior practice.

For certain classes of work the yarn may be given a further treatment. For this purpose, the box 22 is transferred to the right hand end of the apparatus shown in Fig. 2 and the given length of yarn is fed therefrom over a roll 25 and thence downwardly into a vat 26 so as to pass through the reduced indigo liquor containedltherein under the rolls 21 and 28 and thence upwardly through squeeze rolls S'. 'I'he yarn is then passed through the open air above the vat 26 to oxidize the indigo by feeding it upwardly over a roll 29 and downwardly into the reduced indigo solution in the vat 26 where it passes under the rolls 30 and 3! and thence upwardly and between the squeeze rolls S". From the squeeze rolls S" the yarn is passed through the open air above the vat to oxidize the indigo by feeding it over a roll 32 carried by a traverse mechanism T and then downwardly into the box 33. This tinctive appearance and show very little change v in appearance as compared to those in goods made from yarn dyed in accordance with prior practices, thus indicating the completeness of penetration of the dye into the threads. When cloth made from yarn dyed in accordance with the invention is subjected to an abrasion test, for example, by rubbing local spots with sandpaper, no white spots appear thus indicating that the dye has thoroughly penetrated the threads of the yarn.

While the invention has been described in reference to dyeing cotton yarn as such, it is believed that it is equally applicable to dyeing yarn after the yarn has been fabricated to form cloth and also to dyeing other types of yarn either before or after it is formed into cloth.

I claim:.`

l. The process of dyeing previously wettedout cotton yarn with reduced indigo dye liquor by feeding successive` portions of the yarn continuously through a body of said liquor, comprising causing the dye to substantially completely penetrate the yarn by subjecting succesn sive portions to a plurality of submersions by passing the yarn by one end thereof without removing surplus liquor or oxidizing the dye into each submersion in the form of folds in slack condition and without tension until-substantially all of the yarn is submergedLremoving the end of the yarn last to enter each said submersion and passing the yarn by that end into the next succeeding submersion, and oxidizing the dye in the yarn after the last submersion.

2. Process of dyeing previously wetted-out cotton yarn with reduced indigo dye liquorwhich comprises progressively feeding continuous successive portions of the yarn lineally into reduced indigo liquor and submitting the yarn in such manner to successive submersions in reduced indigo liquor, said yarn during said`submersions being in slack condition andwithouttension, and without removing surplus liquor or oxidizing the dye between successive submersions thereby obtaining complete penetration of the yarn by the unoxdized dye, then oxidizing the dye in the yarn and again submerging the yarn, and then removing the surplus liquor and again oxidizing the dye in the yarn, thereby producing a surface coating on the yarn which has already been completely penetrated by the dye.

vvnr'ann c. Foss. 7s 

